1. Field of the Invention
The present invention relates to a fiber reinforced composite material which is effective to reduce vibration and noise when used for a construction body such as a space construction equipment, for example, an artificial satellite, an office automation machine and device, and automobile, a leisure article or the like; and also a process for the production thereof.
2. Description of the Prior Art
Fiber reinforced composite materials are those comprising inorganic fibers such as carbon fibers or glass fibers or organic fibers such as aramid (-aromatic polyamide) fibers integrally combined with a matrix resin such as an epoxy resin, a polyimide resin or a polyether-ether ketone resin.
Such fiber reinforced composite materials, when compared with conventional metal construction materials, have advantages of light weight and high strength and also an advantage that any desired mechanical properties can be obtained by appropriately controlling orientation angles of the fibers. Therefore, the fiber reinforced composite materials tend to be widely used for construction materials particularly for those requiring light weight, such as a space construction equipment, an aircraft, an automobile, a leisure article or the like.
As the use of such composite materials have been broadened, there occurrs a problem of vibration.
Since the fiber reinforced composite materials are lightweight and have a small vibration damping property (of loss factor .eta.=0.001-0.01) to an extent similar to that of conventional metal construction materials, they are liable to vibrate. Further, they are often used for molding a construction body as a whole and so it is impossible to rely upon any vibration damping by friction at connecting portions (constructional damping) differently from conventional metal construction materials. Therefore, in a space construction equipment such as an artificial satellite, problems of troubles of loaded apparatus and lowering of precision of antenna positions occur owing to the vibration of the construction body. It is thus very important to improve the vibration damping property of fiber reinforced composite materials.
Bill Carroll reported, in 33rd International SAMPF. Symposium Mar. 7-10, 1988, improved toughness of carbon fiber composites via the use of thermoplastic interplies. In such construction, however, a thermoplastic sheet having a high Young's modulus and a low vibration damping property at a room temperature is sandwiched between carbon fiber reinforced composite material layers, and so it is expected that the toughness will be improved but it is not expected that any vibration damping properties can be improved.
Takesada Sasaki proposed, in Transactions, ISIS, Vol. 19 (1979), pages 569-577, composites for noise and vibration control-high damping composite steel sheet. In such constitution, a viscoelastic polymer layer is sandwiched between two steel sheets. However, since steel sheets have no anisotropic property, the vibration damping property can be improved only in flexural vibration, but not in stretching vibration.
It is possible to increase vibration damping of a composite material by incorporating a flexibility-attaching agent such as polyethylene glycol, polypropylene glycol or liquid rubber into a matrix resin of the composite material. The vibration damping property of the matrix resin itself can be much improved by such agent, but that of the composite material in its entirety can be only slightly improved by such agent. Further, the stiffness of the composite material is considerably decreased, by such agent. The use of the flexibility-attaching agent therefore, is not effective.